251 – Bennett’s Exhaust Valve Rescue on his Cessna TTx

Bennett contacted me awhile back to see if I could lap an exhaust valve for him.

The #4 exhaust valve showed a very uneven appearance when viewed with his borescope.

Bennett flew in to KSHD one morning and we got started.

Before lapping, we checked the cylinder compression and it was 29/80… not good.

Here’s what the valve looked like:

We got to work and lapped the valve.

When we were happy with the progress, we reinstalled the exhaust valve in the valve guide and installed new valve springs and a new rotocoil, to help ensure the valve would rotate properly and provide the best possibility for a good seal between the valve and the seat.

After running the engine, we rechecked the compression, and were very pleased… it was 74/80!

Amazing!

But there’s more…

Several weeks later, Bennett emailed me, and here’s what he said:

“Dean, I am so excited I am emailing from my hangar… Looks like lapping worked great! After one flight down to Florida and back… about 3.5 hours each way, the #4 exhaust valve looks vastly improved. See before and after pics attached. Much thanks!”

And here are the before and after photos he sent:

BEFORE:

AFTER: (and keep in mind the following photo was after only about 7 hours of engine operation.)

I’m confident this exhaust valve has been rescued, and will quite possibly run normally for many more hours.

It’s always nice when we can solve these valve problems with “laparoscopic surgery” (lapping a valve in place) instead of “major surgery” (removing a cylinder.)

There’s more to this story, but I’m not going to type it out here… you can listen to the audio for this podcast and hear about the magneto issues we solved on Bennett’s engine as well.

(The magnetos on Bennett’s engine are challenging to work on due to their location and all the stuff around them, but with some persistence, it’s doable.)

Thanks Bennett, for flying down to SHD.

It was nice meeting you and working with you!

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